Belt-driven hand saw with increased belt friction



March 1956 A. w. RICHARDS EI'AL 2,737,213

BELT-DRIVEN HAND SAW WITH INCREASED BELT FRICTION 4 Sheets-Sheet 1 Original Filed Feb. 2, 1950 1N VEN TORS.

March 1956 A, w, RICHARDS ET AL 2,737,213

BELT-DRIVEN HAND SAW WITH INCREASED BELT FRICTION Original Filed Feb. 2, 1950 4 Sheets-Sheet 2 v 4 INVENTORS.

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March 6, 1956 A, w. RICHARDS El AL ,7

BELT-DRIVEN HAND SAW WITH INCREASED BELT FRICTION Original Filed Feb. 2, 1950 4 Sheets-Sheet 3 INVEN TORS. 4/!052 W/fi'mwrw BY 157m JOJ rim w QM.

11km, Jana fr March 1956 A, w. RICHARDS ETAL 2,737,213

BELT-DRIVEN HAND SAW WITH INCREASED BELT FRICTION Original Filed Feb. 2, 1950 4 Sheets-Sheet 4 United Sttes Patent BELT-DRIVEN HA ND 'SAWMTH'INCREASED "r BELT FRICTION Archer W. Richards, Chagrin" Falls; and Ei-vin il'i ste'rhus,"--

Cleveland; 0hio,-assignors' to Syntron =0mpany H0mer City, -Pa., -acorporation of Delaware original'ap lieation February], 1950; S erial'No; 14Z,l)66,} l nOWTatent NO.2,671,476,dated March9, 19551;*Di-' vided and this applicati0ri-February-6', 1953; Serial- No". 335,524

1 Claims. (Cl; 143- 43) This'invenfion r'elatesgenerally to motor operated-porn ablehand'saws, 'and'more particularly to belt-driven hand.

saws.

This invehtiohjis a division of application Serial No. 142,066 filed "February 2, '1950, for Portable Belt-Driven- Power HandSaw, "issued March 9, 1954, as -Pat'. Nol

Motoroperatedbelt-driven hand saws have been suggested in the" arta's disc'lo's'ed in Wei'tz, 1,663,486, of

March 2 0, 1928, yet this'saw was not successful comme'rcially probably'owin'g'to' the impracticability of its structure and design. It is obviouslyftoo heavy and l bulky'and difiicult to manipulate. The center of-rnass is not'properly"located relativetothehandle'l It shows aninduction "motor the speed'of whichis les's thanthatof ;the"saw requiringa step-up transmission? A geardrlvedmotor'hahd saw was much smaller "and very neat in design; The gearsaw became very popular, yet the gears Wear out in a relatively'short"time and. they are quite noisy.

The-motor operate'cl'belfidriven hand saw comprising this invention"providesa higher speed series motor that' is light'in weight and readily manipulatable'. The speed is r'edu'cedto thesaw'whichis quiet and'efficient in 'its operation;- The structure of this novelhand'saw permits" it to cut 'in'a planedisposeda'ngular to the' surface of the board being cut. The base ot this saw mayalso be" adjusted"todetermine the 'depth'of the sawcut, all 'of which makes this hand saw less dangerous to handle:

drivethe savvy 'one or-two 'V-b'elts may beem'ployedto increase the nO IoadfrictiOn and 1 reduce the no load speed butincrease'theload transmission.- When oneV-' belt is employed, the belt should run below theperip'hery of the gro'oves'i'n the pulley. Whenusing two beltsythe grooves rnaybe shallow or deep. These structural features provid'elong lift'wi'th durability and permit the transmis-' sion of adequate powerto the saw blade for properly performing its'work." The geartype drive is inadequate for' the transmission of power, particularly'at light loads it sooh'wears'out.

This'belt-driven' hand saw --is provided with spaced cradle sock'ets for-supporting the motor." Th''surfaes on the' inotor which -"are received" inthe cradle sockets" are eccentric to its rotary shaft. The motor is thus pivoted relative-to the base and a slight movement of the motor housin'g' in'creas'es or decreases the distance between-the motor shaft and theblade shaft to 'enable one to adjust thetensio'nonthe belt drive before clamping the motorto the ba'seJ- A spring having a predetermined resistance to fiexure is fastened to the motor and when pushed until it points-1'0 a given mark it tightens the belt means to a predetermined degree.- This provides a constant ten sion on the beltmeans and it may always be-uniformly measured andadjusted regardless-of wear of'the parts:

Another structural characteristic ofthis' belt-driven hand v T 2,737,213 Patented Mar. 6, 1956 2 saw'=i's the' dispbsitiomofthe handle-"relative-to the-center of mass. The motor shaft'and thesaw-bladeshafr'are parallel-and the 'handle' "is above, placing the hand" over the power shaft 2 and *the motor. This arrangement-properly' distributes 'the" Weight of the tool'ma'king' it very easilyhandled =ai1d manipulated:

Anothenobjec't is the"provision of -'a belt-'drivemhand' saw wherein the motor and saw shafts 'are paralleland close together making acompacttool:

Another-" obje'c't of thisinvention is the provision "of a" t simple structure that is economical 'to manufacturer The" tool base "and the wood= engaging' surface together with the several partsof the housing are: simple structur'es'read ily assembled andirnay be die-castingsor stampin'gs. The mo'tor being' mounted under the housing,' needs no' heavyexterior shell. It is in the form of twodeeply drawn-"cups or castings having sockets :for'treceiving the shaft" bearings and the'i'arcuate eccentrics'upporting surfaces may be weld-' i ed or cas't on the ends ofthesecups; Thetmotor'is held!- byia strap" or screw?lock-:whichmaybefloosened to shift the-motor and tighten the belt:

Spacedibearings: in t the longiisleeve' are employed to rotatablytsupport's the :powe'r'ishaft. I v Tli'e 'space betweenazi thezbearings; may. :be packed ?and piled 'through;.the. power shaft;7and:thu's 1 beisealed :oif ibyz the screw: holding: the; saw on the shaft: ".Thez'longisleeve between theibearings 3 adds many: moref hours "of lifelfto the saw. as ,it properly resists lateral. ishocku'such 'as experienced" whenzthegsawis first engages the :material .it is to cut or a hard 'spotduringsz-a the'cutting-ithereof.

Other objects. and advantagesrappear in ;thewfollowingi;.: description and claims; 1

The:accompanying drawings show, for IhELPUIPOSBriOfTI'? exemplification without limiting the invention r01" claimsw thereto; ECertainpractical embodiments. of the invention wherein :m

Fig. 31 is a planuview of'thebelt-driven hand saw com-1 prisingthis invention;

Figs-2 is a.-view inside elevationof the structure shownm in Fig. 1;

Fig.:;3. is a sectionalviewfof thesaw and its arbor;

Fig.4 is a viewrin=horizontalisection of a singlevbeltdrive with parts being broken away;

Fig.3 5 is a view in verticalsection of the structure- 1 shown in Figg't4;

Fig.6 is a viewin horizontal section of-a single cogbelt drive with parts being brokenaway;

Fig. i7-is a-view in .verticalsection of the structure shown-z= in Fig.:6; and

Fig 8 is a graph; of thexspeed v. currentloadfor the-e, three types of belt transmission, single V-belt,. double,:- V-belt and cog belt.

Referring to the drawings, it willbe noted that-the hand saw-comprising this. invention is made up of anwad justable base 1 which is hingedly' attached to the frame; member-2 that supportszthe high; speed'serie's motor: 3 andrthe. saw -shaft 4. The frame member 2 also-. has T the :housingS attached thereto whichis provided.-wit-h-.-;: the :griprhandle .6 andflthe hand knob 7 and-is alsorar av ranged to carry thelupper fixedshield 8 and theFlower. adjustable shield"? for the saw blade 10. The grip handle"6 has a front support guard 63.

The adjustable 'saw base 1 is provided with the aligned hinged s0'ckets"11and 12Lforreceiving the one leg'loft the' 'hinge pi11'13'. The other leg of the ..hinge pin,13 is' pivotal'ly retained'in the aligned 'hinge'sockets '14" and 15"? which are welded to therear endofthe' frame 2.". In" viewof the fact that the single-hinge pin 13*ha's two legs disposed at -"-'toieach other andsince"the'hingesockets ":112'an'cl.f12 are secured'to the base 1, it is obvious that theaouterz endzof thebase 1 may be swung onthe' axes :of ::the E-soekets lliandulzz towam :an'd away from U the frame 2 to provide a relative angular position of the saw blade to the under surface of the base 1. The saw has to be turned in the proper direction to determine the direction of this outer cut relative to a plane normal to the underside of the base 1.

On the other hand, it is also noted that the front end of the base 1 may be swung toward and away from the frame 2 as the base is also pivoted on the other leg of the pin 13 that lies in the hinge sockets 14 and 15. With this adjustment the forepart of the base 1 is moved toward and away from the saw and the rear part is held by the hinge pin in a fixed pivoted position relative to the saw. If the base 1 is close to the underside of the frame 2 it will be parallel therewith and the front end may be moved toward or away from the shaft 4 carrying the saw 10, thereby providing different depths of cut for the saw blade 10. Both the angular and depth adjustment of the base 1 may be made simultaneously relative to the saw blade.

A member 16 is pivotally hinged on the hinge pin 13 intermediate of the sockets 14 and 15 and extends upwardly to support the clamping bolt 17 which rides through the arcuate slot in the arcuate gauge plate 18 which is provided with numerals indicating the angular degree of the underface of the base plate 1 relative to the saw. The bolt 17 is held in any desired position in its arcuate slot by means of the winged clamping nut 19. The center of radius of the arcuate slot is of course taken from the axis of the sockets 11 and 12.

A member 20 is provided with a socket 21 for receiving the outer end of the hinge pin 13 adjacent the socket 11. The member 20 extends upwardly to receive the bolt 22 that is clamped in place by means of the nut 23'. The bolt 22 is adjustable along the slot 24 in the gauge plate 25 which is supported integrally relative to the housing 5 and the arcuate slot 24 has for its center of radius the axis of the sockets 14 and 15 secured to the end of the frame 2. Thus, when the base is pivoted on the axis of the sockets 14 and 15 and the front end swings downwardly to determine the depth of the sawcut, it may be clamped in any desired position along the slot 24 so as to properly gauge the saw relative to the undersurface of the base plate 1.

The extreme front end of the base plate 1 is turned upwardly to form a lip 26 which permits the base to be slid over the wood or a series of boards that might be rough or otherwise uneven in sawing the same, such as sawing off the ends of the roof boards that project beyond the eave of a house. A lateral guage 28 is secured to a stem 29 that is marked as a scale and slides through the socket 30 and may be secured by the set screw 31. The relative position of the gauge 28 and the saw blade 10 may be set by shifting the stem 29 to a desired position and clamping the same by means of the clamping screw 31 in the socket 30.

The parallel cradle surfaces are arranged to receive the tube 35 which is shown in detail in Fig. 3 and contains two bearing sleeve sections 37 and 38. Intermediate the bearing sleeves 37 and 38 an annular oil wick 36 is inserted and may be supplied with oil through the axial and radial passages by removing the saw blade mounting screw 43 which also closes the oil reservoir formed by the axial and radial passages in the shaft 4. The bearing sleeves 37 and 38 have flanges which cover the ends of the tube 35. The saw shaft 4 is arranged to rotate in the composite bearing sleeve mounted in the tube 35. A double grooved pulley 41 is secured to one end of the shaft 4 and a series of fan blades 42 are on the inner face of the pulley for the purpose of creating a draft to circulate air from the left side of the housing 5 toward the saw to cool the pulley and prevent the deposit of sawdust within the housing. The fan prevents quiescence in the housing and any time that sawdust tends to creep in it provides circulation for discharging the same. In this manner the motor and other parts are kept clear of sawdust, yet they are not sealed in and are cooler in operation.

The opposite end of the shaft 4 has the saw blade 10 secured thereto by means of the nut 43, the blade being held between the washers 44. It will be noted that the tube 35 extends beyond the upwardly extending wall of the base 2 for the purpose of functioning to re ceive the bearing sleeve 45 to which is journaled the cover 8. The outer end of the bearing sleeve 45 has the movable shield 9 secured thereto, as indicated at 46, and is permitted to rotate about the axis of the saw. This shield is provided with a spring, to keep the shield 9 in its fully extended position.

The motor 3 is a universal motor being series wound and operating at a speed of approximately twelve thousand R. P. M. It is encased in two cup-like housings, three and three-fourths inches in diameter, as shown at 48 and 49, which are shoved over the ends of the motor field and are provided with flanges that come together, as indicated at 50. Each cup-shaped housing is provided with an arcuate supporting surface, as shown at 51 and 52, which are arranged to rest in the cradles 33 and 32, respectively, of the base 2. A strap member 53 is secured at one end to the base 2, as shown at 54, and extends over the flanges 50, and is also adjustably secured at its other end to the base 2, as indicated at 55, for the purpose of tightly clamping the motor down to the base 2. The motor 3 has a condenser 39 to check radio interference and is likewise provided with a doublegrooved pulley 56 approximately one 'and one-quarter inch in diameter for receiving the belt members 57 and 58 that extend from the motor pulley to the saw pulley 41 which is approximately two and one-half inches in diameter which provides approximately 12,000 surface feet per minute for an eight inch saw blade. The arcuate supporting surfaces 51 and 52 are eccentric to the shaft of the motor end, thus, any relative arcuate adjustment of the motor will determine the tension on the belts 5'7 and 58. It is necessary for one to remove the cover 5 and loosen the strap 53 and shove against the spring 59 until it aligns with the mark 59 to rotate the motor to a position where the tension on the belt is proper and in accordance with the pressure of the flexed springs and then reclamped. This uniform tension on the belts may be made when the motor is stationary or operating the saw. These mating arcuate cradle surfaces may be knurled or roughened to prevent the motor from slipping from its adjusted position.

The principal housing 5 encases the whole of the motor and the majority of the tube carrying the shaft 4 and has attached thereto the separate housing 60 which encloses the belts. The housing 60 joins the housing 5 to lock the latter in position and it is supported by the bracket 61 which is welded to the base 2. The housing 60 is held in place by the bolt 62, as shown in Fig. 1.

The grip handle 6 contains the electric switch actuated by the finger trigger 64. It will be noted that the butt end 65 of the handle is attached to the rear of the housing 5 above end to the rear of the motor 3; whereas the knob handle 7 is secured to the front of the housing ahead of the sleeve 4. This disposition of the handles properly places the center of mass between the handles 6 and 7 thereby permitting the operator to readily manipulate the saw. The wires coming from the current supply in the cable 66 pass into the handle 6 to the switch and thence back to the motor 3. It will be noted that the switch is a double pole switch and both lines are open when the saw is turned on. A third wire in the cable may be used to ground the saw. The cable 66 is provided with a ground wire that is connected to the inside of the handle below the rubber cable bushing and may have a ground clip at its other end.

The saw shaft 4 is parallel to and very close to the shaft of the motor 3 to concentrate the weight directly under the handle 6. This provides a very compact saw with these shafts as close as the size of the pulleys permit without requiring more than two belts. In the structure shown the motor 3 may be adjusted on the arcuate bearing surfaces so that the axes of the saw shaft and motor shafts are from three and one-quarter to three and five-eighths inches apart. This provides three-eighths inch for wear and belt adjustment. The saw shaft housing 35 may be spaced from the motor casing 48, 49 as little as two and three-eighths inches to as much as four and one-half inches since the tubing 35 is approximately one inch in outside diameter; whereas the casing 48, 49 is three and three-quarter inches and the pulleys have a ratio of approximately two and one-half to one. These dimensions provide important factors in the makeup of this belt type portable saw.

In Figs. 4 and 5, a single V-belt 70 is used to transmit power from the motor 3 by the single deep grooved pulleys 71 and 72 on the series motor and saw shafts respectively. The saw shaft pulley 72 has the cooling fan 42 on its inner face to dissipate the frictional heat developed by the belt 70 running in the deep grooves.

In Figs. 6 and 7 a single cog belt 73 is used to transmit power from the motor to the saw shafts. A cog pulley 74 is provided on the motor shaft and a cog wheel 75 is provided on the saw shaft.

In the transmission of power the cog belt has little or no friction losses as compared to the deep grooved pulley single belt drive or double grooved double belt drive, yet all three drives provide smooth operation under load with a cushioning effect between the high torque series motor and the saw blade. It is also possible to use greater pulley ratios and a higher speed motor with the same diameter saw because there is no slippage with a cog belt. A smaller driving pulley and closer centers between the saws and motor shafts may be used with a cog belt which would be impossible with V-belts. However, there are limitations such as the top no-load speed of a saw. A saw blade has a critical no-load speed at which it will flutter and vibrate. This action will probably result in fatigue and cracking. The no-load high speed flutter also causes a rough cutting at the start of the saw stroke which is decidedly undesirable. A saw blade eight and one-half inches in diameter, which is employed on the saws disclosed herein, has a critical flutter at no-load with speed of 7,200 R. P. M. and a definite flutter at 7,400 R. P. M.

The performance curves shown in Fig. 8 illustrate the different speeds attained for different loads from noload to full-load. Curve 76 is the cog belt drive, 77 the deep grooved single V-belt drive and 78 the double V-belt drive. It will be noted that for the same series motor and diameter of pulleys the cog belt drive provides a much higher no-load speed. This is due to the fact that there is no slip and the speed is away above the flutter speed. In order to use this cog belt drive, it would be necessary to increase the pulley ratios and lower the no-load speed.

The deep groove single V-belt drive also has a higher no-load speed because the transmission losses are not high and to use this transmission the pulley ratios would is shown by the curve 78. At no-load the efiiciency is poor and the best speed attainable for the same motor and the eight and one-half inch saw blade is approximately 6,900 R. P. M. which is below the critical flutter speed. However, at a load greater than normal full load, the transmission is substantially as efiicient as the cog belt. Normal load is about ten amperes on these performance curves.

We claim:

1. A hand manipulated power saw comprising a base carrying a motor support and bearing means the axes of which are parallel with each mounted close to the base and to each other, a high speed motor adjustably clamped on said motor support, a rotary power shaft carrying a saw and rotatably supported by said bearing means, pulley means secured to said motor and to said power shaft and having aligned belt grooves with a small pulley on the motor and a large pulley on said power shaft, and belt means connecting said grooves, the grooves of said large and small pulleys having increased area of contact with the belt means to increase the no-load friction for reducing the no-load speed of the saw and for increasing the load transmission.

2. The structure of claim 1 characterized in that the belt means is a single V-belt and said belt grooves are deeper than the depth of the V-belt.

3. The structure of claim 1 characterized in that said belt grooves are two in number for each pulley and the belt means are two in number.

4. The structure of claim 1 characterized in that said bearing means comprises spaced aligned bearings with an enclosed intermediate space that is connected to the exterior through a passage in said power shaft, which passage is closed by a screw attaching the saw to said power shaft.

5. The structure of claim 1 which also includes a spring attached to said motor and having a predetermined resistance to flexure and to be flexed in the direction away from said power shaft to move said motor on said support to tighten said belt means to a predetermined tension indicated by the flexed spring reaching a mark fixed with respect to the motor.

6. A circular power saw comprising a base, a motor member mounted on said base and having a grooved belt pulley, a rotary power shaft member with a saw and a grooved belt pulley and mounted on said base with the pulley grooves in alignment, belt means connecting said grooves, the mounting of one of said members being adjustable to move said one member toward and away from the other member to tighten said belt means, and a spring attached to said movable member and having a predetermined resistance to flexure and to be flexed in the direction away from said other member to tighten said belt means to a predetermined tension indicated by the flexed spring reaching a mark fixed with respect to said adjustable member.

7. The structure of claim 6 characterized in that said spring means is attached to said movable member adjalikewise have to be increased to bring the no-load speed cent to said belt drive.

References Cited in the file of this patent UNITED STATES PATENTS 561,028 Perry May 26, 1896 1,168,139 Young Jan. 11, 1916 1,396,966 Lyon et a1 Nov. 15, 1921 1,464,351 Casey Aug. 7, 1923 1,568,328 French Jan. 5, 1926 1,663,486 Wertz Mar. 20, 1928 1,848,330 Emmons Mar. 8, 1932 2,357,953 James Sept. 12, 1944 2,381,489 Dietz Aug. 7, 1945 2,488,947 Vavrik Nov. 22, 1949 

